Ruiz joined the Cottagers for over £10 million yesterday.
"Bryan has developed strongly in the last two seasons at FC Twente and is of great value to the club," said Munsterman.
"He has been an important part of us in the last two years and the things we have achieved, such as the championship, were an all-time high. His play has led to much interest from foreign clubs.
"Bryan has always had the ambition to play in a major European league and now is the right time he makes the transition to the Premier League. Bryan was for us not one to keep."